The "hockey stick" reconstruction of surface temperature data in the 2001 IPCC report has long been controversial. However, an NRC report published today verified that the rapid rise in temperature represented by the "blade" of the "hockey stick" is accurate, even if we can only be confident about 400 years of the "stick" data.

The NRC panel expressed a high level of confidence that the planet is warmer than it has been for 400 years after a thorough review of scientific studies. Average global surface temperatures in the Northern Hemisphere rose about 1 degree F during the 20th century. "The numerous indications that recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia, in combination with estimates of external climate forcing variations over the same period, supports the conclusion that human activities are responsible for much of the recent warming,” the panel wrote.